This invention generally relates to electric lamps and has particular reference to an improved base and terminal-pin assembly for a fluorescent lamp.
Conventional type fluorescent lamps as currently manufactured are provided with a base assembly at each end that has a pair of hollow brass pins which are staked to the insulator portion of the base and serve as "bi-pin" terminals for the finished lamp. During the lamp-basing operation, the lead wires which extend from the sealed ends of the envelope are threaded through apertures in the tips of the hollow base pins and then trimmed and electrically connected to the pins by either soldering or welding after the base has been placed on the sealed end of the envelope. Due to the small size of the base pins and the random location of the lead wires relative to the sealed ends of the lamp envelope, it is very difficult to align the lead wires with the pins and then thread them through the pin apertures during the basing operation, particularly at the high-production speeds used in the industry. The lead-wire soldering or welding operation also creates manufacturing problems since they both require equipment that is not only costly to maintain but, unless properly adjusted and constantly monitored, frequently produces poor welds or soldered connections with resultant high "shrinkage" rates and losses in both material and labor. Dirt in the pins, insufficient solder flux and dirty welding electrodes also make it very difficult to produce reliable soldered or welded connections on a consistent basis. It would accordingly be very desirable to provide a base assembly and a terminal-pin structure that would eliminate all of the foregoing manufacturing and quality-control problems.
Various proposals for mechanically connecting the lead wires of an electric lamp to a base component have been employed in the prior art. For example, in U.S. Pat. No. 2,771,589 issued Nov. 20, 1956 to Thomas, the lead wires of a fluorescent lamp are mechanically anchored in "pockets" within the plastic base member by force-fitted metal eyelets to provide a recessed-contact type base assembly. In U.S. Pat. No. 3,546,523 to Gilbert, Jr., the lead wires of a circular-shaped fluorescent lamp are connected to the base pins by forcing the ends of the lead wires into the slotted inner ends of base pins that are embedded in the holder portion of a "snap" type base assembly. In U.S. Pat. No. 2,913,697 to Caplis et al, (FIGS. 1-4 embodiment), the lead wires of a "three-light" type incandescent lamp are fastened to the plastic insulator of the base assembly by nails of easily deformed material, such as lead, that are forcibly driven into the insulator and effect an electrical juncture with the clamped ends of the lead wires.
In accordance with the teachings of the aforementioned concurrently-filed application Ser. No. 136,649 of Plagge et al, the manufacturing and quality-control problems associated with the use of conventional fluorescent lamp bases having hollow metal pins that must be threaded over and then soldered or welded to the lead wires are avoided by using pins of solid metal (or tubular pins of tempered sheet-metal) that are dimensioned to effect a force fit with the lead-wire apertures of the plastic insulator portion of the base and concurrently clamp the substantially straight ends of the lead wires (which are disposed in the apertures) in positive electrical engagement with the inserted pins. According to one embodiment of the aforementioned Plagge et al application, the lead wires extend directly from the lamp stem into the insulator apertures and are precut so that the pin-clamped ends of the wires are substantially flush with the outer face of the insulator. The Plagge et al application also discloses and claims another embodiment wherein the base insulator is provided with a second pair of apertures and the lamp lead wires are arranged so that they extend through such apertures, along the outer face of the insulator and then into the pin apertures so that the clamped ends of the wires are located inside the base assembly. While both of these embodiments are satisfactory from a functional standpoint, it has been found that leaving the cut ends of the lead wires exposed at the outer face of the base insulator is rather unsightly and may constitute a potential safety hazard, particularly if the ends of the lead wires are not precisely flush with the surface of the insulator. It would also be desirable to eliminate the additional operation of inserting the lead wires through a second pair of apertures as required by the other embodiment of the Plagge et al application.